1. Field of the Invention
The present invention relates generally to the field of solid-state lasers and, more specifically, to a holmium laser pumped with a neodymium laser.
2. Description of the Prior Art
In solid-state lasers, a light-emitting element is added as a dopant to a compound that serves as a crystalline or amorphous host. The characteristics of the solid-state laser depend on the dopant and crystalline compounds that are selected. The best light emitting dopant materials include chromium, neodymium, erbium, holmium, cerium, cobalt and titanium. One of the most common types of solid-state lasers is that which is made from the neodymium dopant.
All laser materials have characteristic energy levels and transitions so that light is emitted on certain transitions when they drop from excited states. Likewise, the materials absorb light at characteristic wavelengths when they are in the ground state or other low levels.
Absorption can be at a narrow or broad range of wavelengths depending on the transitions involved. Laser operation on the holmium .sup.5 I.sub.6 to .sup.5 I.sub.7, and .sup.5 I.sub.7 to .sup.5 I.sub.8 transitions have been reported at near 2.9 and 2.1 .mu.m in several different host crystals. Holmium has few absorption bands for pumping in the visible and near-IR (infrared). Consequently, laser performances using broad spectral emission pump sources have been poor except where additional sensitizer ions have been used. The .sup.5 I.sub.8 to .sup.5 I.sub.6 holmium absorption spectra for a typical laser host material (Yttrium Ortho-Aluminate) is shown in FIG. 1. In the example, the crystal is 7.8 cm long and contains 2% (atomic %) holmium. Due to the potential medical applications and other commercial uses of 3 .mu.m wavelength lasers, a need exists for an efficient, high power, solid-state pumping source for a holmium laser.